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How do you query for “is not null” in Mongo?
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This will return all documents with a key called "IMAGE URL", but they may still have a null value.
db.mycollection.find({"IMAGE URL":{$exists:true}});
This will return all documents with both a key called "IMAGE URL" and a non-null value.
d...
Minimizing NExpectation for a custom distribution in Mathematica
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As far as I see, the problem is (as you already wrote), that MeanResidualLife takes a long time to compute, even for a single evaluation. Now, the FindMinimum or similar functions try to find a minimum to the function. Finding a minimum requires either to set the first derivative of the function...
Python integer division yields float
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@JonathanSternberg except for all the code that was written for python 2.0. I feel like the role of / and // should be reversed to keep backwards compatibility. Also, in pretty much every other language / preserves type. i would make more sense then fo...
How to disable python warnings
...lter("ignore")
fxn()
I don't condone it, but you could just suppress all warnings with this:
import warnings
warnings.filterwarnings("ignore")
Ex:
>>> import warnings
>>> def f():
... print('before')
... warnings.warn('you are warned!')
... print('after')
>>> ...
undefined reference to boost::system::system_category() when compiling
...raries. I have the 1.46-dev Boost libraries from the Ubuntu Repository installed, but I get an error when compiling the program.
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How do I replace whitespaces with underscore?
...s, such as \t or a non-breaking space.
– Roberto Bonvallet
Jun 17 '09 at 15:49
13
Yes you are cor...
Python __str__ and lists
In Java, if I call List.toString(), it will automatically call the toString() method on each object inside the List. For example, if my list contains objects o1, o2, and o3, list.toString() would look something like this:
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How to open link in new tab on html?
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The special targets all start with an underscore. blank would be the name of a frame or window. It may seem to work, because a new window or tab will probably be opened when none exists with the name 'blank', but a second click on the link shoul...
What does `m_` variable prefix mean?
...'re using something like intelliSense, you can start with m_ and a list of all your member variables are shown. Part of Hungarian notation, see the part about scope in the examples here.
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How to join strings in Elixir?
...your list size is arbitrary:
Enum.join(["StringA", "StringB"], " ")
... all of the solutions above will return
"StringA StringB"
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